1. Field of the Invention
The present invention relates to an inflatable packer assembly for use in a subterranean well bore, and more particularly, to a packer assembly including an inflatable packer and a fluid piston for inflating the packer and to methods of utilizing such assembly.
2. Background Information
Isolation of a cased or uncased interval of a well bore is often desirable to permit the isolated well bore interval and/or a corresponding interval of the subterranean formation penetrated by the well bore to be selectively treated. The cased interval of a subterranean well bore which is isolated is normally perforated, although occasionally it may be desirable to isolate an unperforated interval of casing, e.g., to test the unperforated interval for fluid leaks.
Conventionally, a packer is positioned at the lower end of a tubing string and is usually secured against axial movement within a well bore by means of slips which are mechanically expanded, such as by means of a wedge, into contact with casing. Once positioned in the well bore, subsequent rotation and downward movement of the tubing string mechanically expands the packer into contact with the casing. These conventional, mechanically set packers are normally sized slightly less than, e.g. 1/8 to 1/4 inch, the internal diameter of the casing within which they are positioned. Further, the sealing element of a conventional mechanical packer is relatively short, e.g., one foot or less. Upon expansion, the expanded packer element engages and seals the annulus between the tubing string and casing against fluid flow. Use of such conventional mechanically inflatable packer assemblies to isolate within a perforated casing interval for selective treatment has proved troublesome. The relatively short length of the conventional packer sealing element permits unconsolidated matrix, i.e., sand, from the subterranean formation which is penetrated by the well bore to flow through that portion of a perforated interval which is located above the inflated packer and be deposited on top of the packer. Upon completion of a given operation, the mechanical packer is retracted. However, the extremely close tolerance between the external diameter of the retracted packer and the internal diameter of the casing often permits sand and/or other objects within the well bore to become lodged between the retracted packer and/or the retracted slips and the casing thereby causing the mechanical packer to become stuck within the well bore. Retrieval of a stuck mechanical packer is difficult, time consuming and expensive. Accordingly, mechanical packers are normally not employed in a perforated interval of casing or an uncased section of a well bore.
Conventional inflatable packers have been proposed for use in lieu of mechanical packers to isolate a given cased or uncased well bore interval. Inflatable packers employ valve assemblies which in conjunction with fluid pressure within the well bore inflate and deflate the packer element. Multiple inflation of such packers is difficult to obtain due to structural constraints of the valve assembly and difficulties in ascertaining and obtaining requisite tubing fluid pressures. Further, such inflatable packers conventionally are inflated with fluid housed within a tubing string and isolated from well bore fluids. Thus, changes in temperature of and/or hydrostatic pressure exerted upon such isolated tubing fluid expand the fluid creating problems due to overinflation of the packer. Thus, a need exists for an inflatable packer assembly which is capable of being repeatedly inflated and deflated and repositioned within a cased or uncased section of a subterranean well bore.
Accordingly, it is an object of the present invention to provide an inflatable packer assembly which can be easily inflated and deflated using well bore fluid and repositioned within a well bore.
It is another object of the present invention to provide an inflatable packer assembly having a fluid piston which can be manipulated to inflate a packer element and which is located together with a hanger assembly at a sufficient distance from the packer element to ensure against the slips of the hanger assembly and the fluid piston becoming stuck within the casing due to debris flowing into the well bore.
It is also an object of the present invention to provide an inflatable packer assembly which can be repeatedly inflated and repositioned within a well bore without being damaged due to overinflation.
It is a further object of the present invention to provide an inflatable packer assembly which can be utilized to inflate more than one packer in a well bore.
It is a still further object of the present invention to provide a process for treating a relatively long interval of a well bore.